Compact luminaire enclosure

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application under 35 U.S.C. § 119(e), claims priority to and benefit from U.S. Provisional Application No. 60/806,248, which was filed on Jun. 29, 2006, entitled, “Compact Luminaire Enclosure,” which is currently pending, naming all the individuals listed above as inventors, the entire disclosure of which is contained herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a compact luminaire enclosure. More particularly, the present invention relates to a compact luminaire enclosure designed to dissipate heat such that it can be used safely with a 50 watt lamp.

2. Background of the Invention

Manufacturers are continually struggling with external luminaire enclosure temperatures that exceed the recommended maximum safety practices. Since luminaires give off a good deal of heat, which rises, typically the affected surfaces are the internal and external luminaire enclosure surfaces above the light source. This problem can be exacerbated if the luminaire enclosure opening should become covered.

Luminaire enclosures can be made from a variety of materials, but they are often made of plastic. A luminaire enclosure constructed from plastic generally requires a large volume of air to effectively manage heat emanating from the lamp & electronics. When a plastic enclosure experiences the cyclic heating and cooling conditions that result from periodic use of the luminaire, the chemical bonds within the molecules of plastic begin to weaken or break. Once these bonds begin to break, the breaking process accelerates at an exponential rate, thereby degrading the physical and mechanical properties of the plastic enclosure very quickly.

When the structure of the enclosure weakens and breaks down, the enclosure can no longer effectively dissipate heat. The heat produced by the luminaire becomes more and more concentrated within the enclosure over time, which causes the luminaire to exceed its maximum operating temperature. Eventually, this leads to the premature failure of the electronic components of the luminaire or the enclosure itself, or perhaps both.

In addition to the mechanical failure described above, the poor thermal management qualities of plastic luminaire enclosures and excessive internal and external enclosure surface temperatures can result in the failure to obtain third party safety agency listings and approvals. Non-acceptance of local government agencies, national government agencies, and other requirements set forth by national, state, or local regulations can result in lost sales for manufacturers.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a compact luminaire enclosure that dissipates heat effectively.

It is a further object of the invention to provide a compact luminaire enclosure with an internal thermal heat shield.

The invention generally comprises a compact luminaire enclosure that has about 14 to 18, and preferably 16, cubic inches of air volume and can be used safely with a 50 watt lamp. The luminaire enclosure comprises a housing and a shroud that is removably attached to the housing. The shroud has a non-planar face that prevents the shroud from laying flat and trapping heat if the enclosure is placed against or falls on a flat surface. The housing may be made of at least a portion of polyetherimide, which has very good heat dissipation properties. The shroud may similarly be made of at least a portion of polyetherimide.

The compact luminaire enclosure of the present invention further comprises an internal thermal lamp shield recessed within the housing. The internal thermal lamp shield comprises highly specular material so that it is able to reflect the heat coming from an enclosed lamp. In one embodiment of the invention, the internal thermal lamp shield comprises aluminum covered with glass that has been electrodeposited or sputtered onto its surface, although in another embodiment, the aluminum is anodized.

In one embodiment of the invention, the internal thermal lamp shield is part of a lamp holder assembly comprising a spring clip lamp holder, a lamp holder thermal shield, and a bi-pin lamp holder. In one embodiment of the invention, the lamp holder assembly further comprises two standoff screws that extend through two standoff screw tubes and connect the lamp holder assembly to the enclosure. The various parts of the lamp holder assembly and their arrangement facilitate heat dissipation effectively.

Generally, the structure and design of the compact luminaire enclosure described herein lowers the external enclosure surface temperature, which provides a significant improvement over prior art enclosures. The internal thermal lamp shield and the use of polyetherimide thermal plastic materials allow the enclosure to effectively lower inside and outside thermal plastic enclosure surface temperatures, which increases safety and decreases the likelihood of mechanical failure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of the enclosure with the luminaire, and shroud;

FIG. 2 is a perspective view of the shroud;

FIG. 3 is a side view of the shroud set against a flat surface;

FIG. 4 is an exploded view of the luminaire and lamp holder assembly;

FIG. 5 is a perspective view of the internal thermal lamp shield and lamp holder assembly;

FIG. 6 is a perspective view of the luminaire, the lamp holder assembly, and the internal thermal lamp shield;

FIG. 7 is a front perspective view of the enclosure without the luminaire and shroud; and

FIG. 8 is a front perspective view of the enclosure with the internal thermal lamp shield in a rotated position.

WRITTEN DESCRIPTION

While this invention is capable of embodiments in many different forms, the preferred embodiments are shown in the figures and will be herein described in detail.

The present disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the embodiments illustrated.

Referring now to the drawings, and specifically to FIG. 1, a compact luminaire enclosure 1 comprises a housing 2 and a shroud 4 that is removably attached to the housing 2. In one embodiment, the housing 2 measures between two and four inches in diameter, preferably three inches, at its opening 3 and tapers for a distance of between one and three inches, preferably two inches, to a diameter of between one and three inches, preferably 2 and ¼ inches, at its spherical closed back portion 34. In one embodiment, the shroud 4 is between one and three inches long. The dimensions of the housing provide between 14 and 18 inches of cubic air volume, and preferably 16 cubic inches of air volume, in order to mount enclosed components within it.

As shown in FIG. 2, the shroud 4 has a non-planar or non-flat face 6 that prevents the shroud 4 from trapping heat if the enclosure 1 is placed or falls on a flat surface, such as the ground. Enclosures in the prior art generally had flat, planar faces, which caused problems with overheating. If an enclosure has a flat face, it may lie flat on the ground and trap heat near the luminaire, thereby causing the luminaire to exceed its operating temperature.

The non-planar design of the shroud 4 of the invention helps to prevent the stoppage of airflow and excessive heat build up around the face of the enclosure 1 if it should ever be in this blocked position. As illustrated in FIG. 3, if the compact enclosure should fall on a flat surface 200, the edge 220 of the face 6 rests on the flat surface 200, but since the face 6 is non-planar, it is impossible for the shroud 4 to lay completely flat and trap heat. Instead, one or more venting spaces 210 comprising the open areas between the flat surface 200 and the non-planar face 6 exists when the edge 220 of the face 6 touches the flat surface 200. In the embodiment of the invention shown in FIG. 3, the non-planar face 6 is gently convexly curved from a first end 6a to a second end 6b and has a flat end 6c and flat lower end 6d extending rearward from each respective end. This gentle curve extending between the flat ends 6c, 6d provides an appealing appearance while also increasing the heat venting capability of the shroud 4. Many other non-planar designs would be suitable for the invention.

Referring again to FIG. 2, the shroud 4 inserts into the housing 2 and is held in place by a compression fit and a retaining screw 110, shown in FIG. 7. The shroud has two O-ring grooves 112, 114 and a retaining groove 116. O-rings fit into the two grooves 112, 114 closest to the housing, and the retaining screw 110 fits into the retaining groove 116 and holds the shroud 4 in place. The retaining groove 116 runs along the entire circumference of the shroud 4 so that the shroud 4 can be rotated easily by loosening the retaining screw 110, adjusting the shroud 4, and retightening the retaining screw 110 in the retaining groove 116.

The housing 2 preferably is made of polyetherimide—Ultem® produced by GE Plastics, for example—and the shroud 4 may be made of polyetherimide as well. When polyetherimide is used in the housing of a luminaire enclosure, especially a compact luminaire enclosure such as the enclosure 1 of the invention, the housing maintains its appearance and structure much better over time. Importantly, polyetherimide has a higher glass transition temperature than other materials, such as polyphenylene sulfide, that have previously been used in luminaire housings. Once a particular material reaches its glass transition temperature, its component molecules move around more freely, its chemical bonds begin to weaken, and the overall strength of the structure begins to decline.

Because luminaire enclosures are in close proximity to a heat source, they need to be made of materials that have high glass transition temperatures. In older enclosures, once the temperature of the housing exceeded the glass transition temperature, small pieces of fiberglass or other materials in the enclosure made their way to the surface and formed unattractive small bumps and discoloration on the housing. This effect also led to further degradation of the housing structure because it caused moisture to wick into the housing. With a polyetherimide housing, the enclosure is able to maintain its appearance and effectiveness for an extended period of time.

Referring once more to FIG. 1, in order to further prevent heat from an enclosed luminaire from excessively heating the housing, the compact luminaire enclosure 1 of the present invention comprises an internal thermal lamp shield 50 disposed within the housing 2 such that it reflects thermal energy from the lamp 10 away from the top portion of the enclosure 1.

Referring now to FIGS. 4 and 5, in one embodiment of the invention, the internal thermal lamp shield 50 is part of a lamp holder assembly 20 that is specially designed in order to dissipate heat such that the enclosure 1 maintains a low temperature. The lamp holder assembly 20 has a spring clip lamp holder 22, two threaded standoff screws 24, a bi-pin lamp holder 26, and a lamp holder thermal shield 28. The spring clip lamp holder 22 has two spring clips 23 that project out from the holder 22. When the spring clips 23 are fastened to the lamp holder thermal shield 28, the clips 23 extend through the internal thermal lamp shield 50 and interconnect it with the shield 28 and the holder 22. The spring clips 23 attach to the lamp 10 and hold it in place. In FIG. 4, the lamp 10 supported by the lamp holder assembly 20 comprises a reflector portion 12 and a plug or back portion 14 having two pins 16. The plug portion 14 of the lamp 10 protrudes through the spring clip lamp holder 22, the internal thermal lamp shield 50, and the lamp holder thermal shield 28 so that they surround the plug or back portion 14. Bi-pin lamp holder 26 has electrical holes 31 and wires 33 that are used to connect the lamp 10 to an energy source (not shown). The pins 16 extend through electrical holes 31 of the bi-pin lamp holder 26 and make an electrical connection.

As can be seen more clearly in FIG. 5, the threaded standoff screws 24 do not attach to the lamp 10, but instead hold the lamp holder assembly 20 together by extending through the spring clip lamp holder 22, the internal thermal lamp shield 50, the lamp holder thermal shield 28, the bi-pin lamp holder 26, and insert into the two clinch pin standoff screw tubes 32. In the embodiment shown in FIG. 5, the screws 24 protrude beyond the standoff tubes 32, which allow the screws 24 to attach to the housing 2. The additional surface area of the standoff screw tubes 32 dissipates heat into the cooler back portion 34 (see FIG. 1) of the luminaire enclosure 1, thereby helping to lower the enclosure temperature near the lamp 10 and therefore preferably are constructed of a heat conducting material.

FIG. 4 shows two O-ring retainers 70 that are adaptable to slide over the screws 24 when the lamp holder assembly 20 is constructed. The O-ring retainers 70 hold the lamp holder assembly 20 together for easy installation, and they also break the direct thermal conduction between the standoff tubes 32 and the housing 2.

The order of the components of the lamp holder assembly 20 breaks the direct thermal conduction between the internal thermal lamp shield 50 and the bi-pin lamp holder 26. The lamp holder thermal shield 28 and the internal thermal lamp shield 50 minimize the conduction of thermal energy to the bi-pin lamp holder 26, thereby allowing the bi-pin lamp holder 26 to operate below its maximum suggested operating temperature while the lamp 10 is positioned in any mounting orientation. The ability to provide for limitless mounting orientation without over-heating the bi-pin lamp holder 26 greatly enhances the utility of the enclosure 1. Maintaining lower temperatures within the enclosure 1 helps prevent premature component failure and therefore increases luminaire life and reliability. The heat-dissipating design of the compact luminaire enclosure allows it to be used with lamps that produce a great deal of heat, such as a 50 watt MR-16 type lamp.

In one embodiment, the spring clip lamp holder 22 is made of stainless steel. The use of a stainless steel spring clip as the lamp holder 22 helps prevent clip corrosion and loss of spring tension, and it also provides a positive vibration-proof lamp grip in any luminaire mounting orientation without lamp breakage. The spring clip lamp holder 22 of the invention has two functions: it acts as a heat sink and it also maintains the position of the luminaire 10.

Returning now to a discussion of the internal thermal lamp shield 50, as shown in the embodiments of FIGS. 4, 5, and 6, the internal thermal lamp shield 50 comprises an oval-shaped base ring 52 having a central aperture 53 that has a top end 54 and a bottom end 56. Extending from the peaked top end 54 of the oval-shaped base portion 52 is a rectangular linker portion or support arm 58 comprising a first end 60 and a second end 62. The first end 60 of the support arm 58 extends from the peaked top end 54 of the oval-shaped base portion 52 into an arcuate shield 64 surrounding at least a portion of the lamp 10. In one embodiment, the shield 64 comprises one or more protective faces 64 that fan out from the support arm 58 and extend over the lamp 10 to redirect thermal energy that would otherwise heat up the surface of the housing 2. The O-shaped base portion 52 is situated within the lamp holder assembly 20 so that the internal thermal lamp shield 50 extends above and past the lamp 10. In this embodiment of the invention, the faces 64 of the internal thermal lamp shield 50 fan out and partially surround the lamp 10 in order to block and redirect heat that would otherwise hit the housing 2 of the enclosure 1.

The internal thermal heat shield 50 preferably comprises specular finished materials that enable the shield to direct thermal energy away from the enclosure 1. These specular materials include, for example, aluminum coated with glass that has been sputtered or electrodeposited on its surface.

The internal thermal lamp shield 50 is also preferably rotatable about the lamp holder assembly 20. FIG. 7 shows the compact luminaire enclosure 1 of the invention with the internal thermal lamp shield 50 in one orientation. In contrast, FIG. 8 shows the internal thermal lamp shield 50 in a different orientation than that shown in FIG. 7, which demonstrates the rotatability of the shield 50. This rotatability allows the internal thermal lamp shield 50 to be maintained in virtually any position around a luminaire while it is in use. In order to adjust the internal thermal lamp shield 50, the standoff screws 24 can be loosened so that the thermal shield 50 can be rotated and fixed in another position even while the lamp 10 is still attached to the rest of the lamp holder assembly 20. The pins 16 of the lamp 10 attach to the bi-pin lamp holder 26 and protrude through the circular aperture 53 in the middle of the internal thermal lamp shield 50 without being directly attached to the lamp shield 50, which leaves the lamp shield 50 free to rotate around the pins 16 once the standoff screws 24 are loosened.

While there have been described what are believed to be the preferred embodiments of the present invention, those skilled in the art will recognize that other and further changes and modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the true scope of the invention.